Just signal boosting this again. As of March 15, 2017 Dropbox changed the Public folder to private. Any public links you may have shared over the interwebs are now broken. You will need to create a new public link again to allow others access.

Because of this change, it may be possible that a lot of user submitted resources are no longer available. That includes any scripts, images, or projects. Please try to contact the topic owner of any broken Dropbox links.

But I do agree that this is a pretty huge dick move by them. I don't understand why this change needed to happen and why it was forced upon everyone. Especially for communities like us, this just adds to the headaches.